The proposed research involves the development and field testing of a questionnaire designed to measure involuntary exposure to tobacco smoke. There are two distinct parts to the proposed study design. The first part of the study involves an evaluation of the validity of questionnaire reports of recent tobacco smoke exposure. Urinary cotinine will be used as an objective indicator of recent environmental tobacco smoke exposure. Study subjects will include 1,500 nonsmokers recruited from among persons attending the Prevention-Detection Center at Roswell Park Memorial Institute. Subjects will be questioned about their exposures to other people's tobacco smoke occurring during the four days preceding the interview. Various self-reported measures of exposure to tobacco smoke (e.g., duration, frequency, location) will then be correlated with urinary cotinine levels to identify which questionnaire measures best predict tobacco smoke exposure. The second part of the study involves an investigation of the reliability of questionnaire reports of present and past exposure to tobacco smoke. The same 1,500 subjects interviewed in part 1 of the study, will be questioned about present and past exposure to tobacco smoke at home, at work, and during childhood. To assess the reliability of subject exposure information surrogates for home, work, and childhood exposures will be identified and interviewed to collect comparable exposure data. The findings from this research will help identify factors important to consider in defining exposure to passive smoke and will provide an assessment of the reliability of self-reported exposure information. Ultimately, the findings from this research will lead to the development of more accurate measures of environmental tobacco smoke exposure and more precise assessments of the health effects of such exposure.